If you are already in this situation, the only cure is to do a manual, clean uninstall first, and then reinstall zdesktop. Your data will not be lost if you follow the steps outlined in Yahoo! Zimbra Desktop - Zimbra :: Wiki

It is a NAB - Norton AntiBot problem- NAB says that it removing MALWare and the way to save the settings is to open NAB, open up control center and under the advance tab, restore Zimbra Desktop.
The question remains - why does NAB conside Zimbra Desktop Malware?